1. Field of the Invention
The invention relates to a skin cleansing composition containing acyl isethionate as surfactant, especially a composition in the form of a toilet bar.
2. The Related Art
Every day all of us wash our hands, and usually with the aid of a cleansing composition. This frequency of use places important demands on the cleanser. Simply delivering a cleansing effect is insufficient. Compositions must be skin friendly, causing little or no irritation, must allow retention of natural dermal oils and must avoid a dry feeling that would leave skin unpleasantly taut. Traditional soaps, i.e. alkalimetal fatty acids, fail in meeting these criteria.
Synthetic detergents are well known and have achieved increasing popularity. Selected types of synthetic detergents have proved much milder than soap but have failed in other properties. Sometimes lathering characteristics are poor. When in the form of a toilet bar, the more popular mild synthetic detergents exhibit such undesirable properties as bar softening leading to mush and excessive wear rates. Manufacturing difficulties are often also found with bars based on synthetic detergents.
Acyl isethionates have risen to a preeminent position among synthetic detergents within the toilet bar category. Dove.RTM. and Caress.RTM. have achieved market leadership in the USA beauty bar category mainly because their major ingredient, sodium cocoyl isethionate, is much milder than soap and provides an exceptional lather. These characteristics have been described in U.S. Pat. Nos. 2,894,912 (Geitz), 3,879,309 (Gatti et al.), 3,951,842 (Prince et al.), 4,180,470 (Tokosh et al.) and 4,260,507 (Barrett) all assigned to Lever Brothers Company and suggesting solutions to improve the aforementioned problems. In U.S. Pat. No. 4,198,311 (France et al.) sodium cocoyl isethionate toilet bars have been improved through the use of at least 1% sodium isostearyl lactylate to achieve such skin conditioning properties as non-oiliness, silkiness, smoothness and non-powdery feel following rinsing and drying.
Improvements in bar firmness through use of additives such as behenic acid have been reported in U.S. Pat. No. 5,262,079 (Kacher et al.).
Reduction of mush/wear has been obtained through combination of acyl isethionate with a major amount of soap. Mildness is only slightly compromised while mush/wear properties dramatically improve. Lever 2000.RTM., a commercially successful deodorant bar in the USA, is based on the aforementioned technology more fully described in U.S. Pat. No. 4,695,395 (Caswell et al.).
Acyl isethionates are mild surfactants, as previously noted. Certain types of additives have been reported which boost mildness into the so-called ultra range. For instance, U.S. Pat. No. 4,673,525 (Small et al.) incorporates moisturizers such as certain sodium acyl lactylates, and polymeric skin feel aids such as cationic polymers. Incorporation of these additives can often adversely affect bar firmness. It would be desirable to obtain a toilet bar based upon acyl isethionate surfactants which exhibits the highest level of mildness while not compromising firmness.
Accordingly, it is an object of the present invention to provide a toilet bar whose major surfactant is acyl isethionate and is ultra mild to the skin.
Another object of the present invention is to provide a toilet bar whose major surfactant is acyl isethionate and exhibits improved firmness with less mush and lower wear rates.
A still further object of the present invention is to provide a toilet bar whose major surfactant is acyl isethionate and exhibits improved moisturization and lathering properties.
These and other objects of the present invention will become more readily apparent upon review of the summary, detailed description and examples which follow.